1. Field of the Invention
The present invention relates to a bulb socket and a terminal installed on the bulb socket for use in the light of an automobile and more particularly to a cathode terminal installed on the bulb socket and electrically connected with the cathode of the bulb.
2. Description of the Related Art
In this kind of bulb socket, a metal plate is bent to form an cathode terminal 1 to be connected with a socket 2 as shown in FIGS. 20 and 21. The cathode terminal 1 is cut in the vicinity of one end thereof in the configuration of U to project a strip elastically therefrom. Thus, a connection strip 1a to be connected with a bulb 3 is formed. A connection strip 1b to be connected with a connector is formed on the other end of the terminal 1. As shown in FIG. 22, the terminal 1 is inserted into a sectionally T-shaped groove 2c formed on the peripheral wall 2b of a bulb inserting hole 2a of the socket 2. The leading end of the connection strip 1a projecting inwardly from the inserting groove 2c contacts the cathode surface of a mouth piece 3a of the bulb 3 inserted into the bulb inserting hole 2a.
A cathode terminal 4 is inserted into an cathode terminal inserting groove 2d opposed to the anode terminal inserting groove 2c. A connection strip 4a of the anode terminal 4 is connected with the anode disposed on the bottom surface 3d of the bulb 3 and the other connection strip 4b of the anode terminal 4 is connected with the connector.
Pins 3b and 3c projecting from the peripheral surface of the mouth piece of the bulb 3 are inserted downwardly into J-shaped pin inserting grooves 2e (one of which is visible in FIG. 22), respectively formed on the peripheral wall 2b of the socket 2. Then, the bulb 3 is rotated to mount it on the socket 2.
The pin inserting grooves 2e formed on the peripheral wall 2b of the socket 2 are opposed to each other so that the position of each of the pin inserting grooves 2e corresponds with the position of each of the pins 3b and 3c of the bulb 3. That is, the peripheral wall 2b of the socket 2 has four inserting grooves formed therein, namely, the groove 2c for receiving the anode terminal 4 opposed to the groove 2d for receiving the cathode terminal 1 and the pin inserting grooves 2e opposed to each other.
The inserting grooves 2c and 2d are approximately T-shaped and open in a small width on the inner surface of the peripheral wall 2b. The inserting groove 2c has a width large enough for the connection strip 1a to project inwardly while the width of the inserting groove 2d is very small.
The pin inserting grooves 2e are sectionally U-shaped and have a width large enough for the pins 3b and 3c to be smoothly inserted thereinto. More specifically, the width of the pin inserting grooves 2e is larger than that of the opening of the inserting groove 2d for receiving the anode terminal and smaller than the outer diameter of the pins 3b and 3c.
Accordingly, the pin 3b or the pin 3c cannot be inserted into the inserting groove 2d because the width of the inserting groove 2d is small. However, the socket 2 is easily deformed, i.e., the width of the opening portion of the inserting groove 2d becomes larger because it is made of resin. As a result, the pin 3b or 3c may be inserted into the inserting groove 2d. As described above, the pins 3b and 3c are opposed to each other. Therefore, the other pin 3b or 3c is inserted into the inserting groove 2c.
As a result, the spring of the terminal is deformed, thus pressing the pin 3b into a portion below the connection strip 1a of the cathode terminal 1 and consequently, the pin 3b is caught by the connection strip 1a. Therefore, the bulb 3 cannot be taken out from the socket 2.
If the inserting grooves 2c and 2d are not opposed to each other, it is necessary that the configuration of the terminals are complicated and dimension accuracy cannot be obtained, and hence manufacturing cost is high. In addition, supposing that the pin 3b or the pin 3c of the bulb 3 is inserted into the cathode terminal inserting groove 2c or 2d, the pin 3b or the pin 3c is brought in contact with the inner surface, of the peripheral wall of the bulb inserting portion, which is not a groove-formed position but the socket 2 is deformed outwardly because the socket 2 is made of resin. As a result, the pin 3b or 3c is pressed into the inserting grooves 2c or 2d. Consequently, the bulb 3 is erroneously inserted into the socket 2.
Thus, even though the configurations of the terminals are complicated and the inserting grooves 2c and 2d are not opposed to each other, an erroneous insertion of the pin 3b or 3c into the inserting groove 2c or 2d cannot be effectively prevented.